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A year of consistent exercise appears to rejuvenate the brain – but don’t ask scientists how yet In A Nutshell

Adults who exercised 150 minutes weekly for 12 months showed brains that appeared seven months younger on structural scans

Scientists can’t explain why it worked. Despite measuring fitness levels, body composition, blood pressure, and brain proteins, none of these factors accounted for the brain age changes, leaving the mechanism a mystery.

Before any exercise began, people with better cardiovascular fitness already had younger-looking brains, nearly two years younger for each meaningful fitness improvement.

Your 30s, 40s, and 50s represent a critical window when exercise might protect against dementia risk decades later, and this study shows moderate activity levels are enough to make a difference.

Committing to an exercise regimen isn’t easy, but a younger brain is a strong motivator. When researchers asked middle-aged adults to practice aerobic exercise regularly for a year, their brains became significantly “younger,” so to speak.

After 12 months of regular workouts, participants’ brains appeared about seven months younger than when they started. MRI scans analyzed by machine learning algorithms showed measurable structural changes associated with younger brains.

Scientists checked several likely explanations for why this may have happened, and none of them panned out. Fitness improved. Blood pressure didn’t budge. Weight stayed the same. Brain growth factors didn’t show clear changes. None of those factors accounted for the brain age shift.

“The pathways by which these effects occur remain unknown,” researchers from the University of Pittsburgh and AdventHealth Research Institute wrote in the Journal of Sport and Health Science.

The study tracked 130 adults between ages 26 and 58, none of them particularly active to start. Half were assigned to an exercise program, half to a control group that just received general health information. The exercise group committed to 150 minutes of moderate aerobic activity per week, the same recommendation countless doctors give to their patients. Two sessions per week happened in a university lab with supervision, and the rest at home (walking, jogging, treadmills, bikes, ellipticals, etc.).

What Brain Age Actually Measures

To better understand “brain age,” researchers fed thousands of MRI scans into a computer, teaching it what a typical 30-year-old brain looks like versus a typical 50-year-old brain. The patterns involve brain volume, structure, and other subtle neurological features.

When someone gets a brain scan, the computer predicts their age based purely on what it sees. If you’re 45 but your brain looks more like that of a typical 48-year-old, you’re aging faster than average. If your brain looks 42, you’re aging slower.

In other studies, each extra year on this brain-aging measure has been linked to about a 3% higher risk of developing dementia down the road. People whose brains look older than their age tend to die earlier and show cognitive decline sooner. Your brain age in midlife may be forecasting your mental sharpness in your 70s and 80s.

Even before the study began, fit participants’ brains appeared younger. (© Leslie Rodrigue – stock.adobe.com) The Fitness Connection Nobody Can Explain

Before the study started, researchers found something in the baseline measurements. People who were more fit had younger-looking brains. For every meaningful bump in measured cardio fitness, brain age looked nearly two years younger on average.

So when the exercise group got fitter over the year (and they did, measurably) researchers expected that would explain everything. It didn’t. Yes, fitness improved. Yes, brain age dropped. However, the statistical analysis showed fitness improvements didn’t account for the brain changes.

Body composition? No change in either group. Blood pressure? Same story. BDNF, a protein often linked to brain health, didn’t show a clear, meaningful increase in exercisers, and it didn’t explain the brain age changes anyway.

The researchers ticked through the usual suspects they’d measured. Nothing added up.

“That was a surprise,” said lead author Dr. Lu Wan, a data scientist at the AdventHealth Research Institute, in a statement. “We expected improvements in fitness or blood pressure to account for the effect, but they didn’t. Exercise may be acting through additional mechanisms we haven’t captured yet, such as subtle changes in brain structure, inflammation, vascular health or other molecular factors.”

What Might Be Happening (Besides What They Measured)

Of course, the brain doesn’t exist in isolation. Exercise triggers a cascade of changes throughout the body, and researchers only measured a handful of possibilities.

Maybe exercise altered inflammatory signals in ways the study didn’t capture. Perhaps it improved blood flow to the brain through mechanisms that wouldn’t show up in simple blood pressure readings. Mitochondria, the tiny power plants in cells, might have gotten more efficient. Metabolic changes could have occurred that weren’t tracked.

Alternatively, brains may have responded to exercise through pathways science hasn’t fully mapped yet. The study wasn’t designed to measure every possible mechanism, just the most obvious candidates.

What researchers do know is that 150 minutes of weekly aerobic exercise (two and a half hours, broken up however one wants) was enough to produce measurable changes in brain structure within a year.

Why Your 30s, 40s, and 50s Matter

Most brain aging studies focus on people in their 70s and 80s, after cognitive decline has already started. This study deliberately targeted younger adults because midlife appears to be a pivot point.

Risk factors that show up in your 40s (high blood pressure, obesity, inactivity) predict dementia risk 20 or 30 years later. But midlife is also when intervention might matter most. Your brain is still resilient enough to respond, but aging processes have begun.

The participants in this study weren’t elderly, weren’t sick, and weren’t already showing cognitive problems. They were regular people, two-thirds of them women, averaging 41 years old. Most were sedentary, reporting less than 100 minutes of exercise per week before the study started. In other words, they looked like a lot of American adults.

Their brains at the study’s start were aging normally on average, though individual participants varied quite a bit. Twelve months of exercise changed that trajectory.

The Exercise Program That Worked

Nothing about the workout regimen required a gym membership or special equipment. Participants walked, jogged, or used whatever cardio equipment they had access to. Heart rate monitors ensured they worked hard enough, breathing heavily but still able to talk, working at about 60-75% of their maximum heart rate.

The group stuck with it remarkably well. They completed 93% of their prescribed exercise minutes. Lab attendance hit 73%, and people made up the difference at home.

Meanwhile, the control group’s fitness declined slightly over the year, as tends to happen when sedentary people stay sedentary. Their brain age drifted slightly upward on average.

The pandemic also complicated things. Some participants couldn’t complete final assessments, and for several months in 2020, lab sessions shut down entirely. Still, 89% of the exercise group returned once facilities reopened, and the results held.

This graphic highlight key findings showing that regular aerobic exercise was associated with a younger-appearing brain on MRI compared with no change in activity. Participants who exercised showed reductions in brain age alongside improved fitness, while no single biological factor fully explained the effect, suggesting multiple pathways may support exercise-related brain health benefits. (Credit: Dr. Kirk I. Erickson from AdventHealth Research Institute, USA Image source link) What This Means for Your Brain

Previous studies showed brain age could be rolled back with extreme interventions: intensive diet and exercise programs in people with obesity, or bariatric surgery. This study extends that finding to healthy, middle-aged adults performing moderate exercise.

The practical takeaway is straightforward: the exercise recommendation you’ve heard a thousand times (150 minutes of moderate activity per week) appears to be enough to change your brain’s aging trajectory. No marathons or endless hours in the gym required.

Ultimately, though, the scientific mystery remains. Exercise changed brain structure in ways that made 40-year-olds’ brains look younger, and researchers still can’t pinpoint the mechanism. That’s not a weakness of the study. It’s a reminder of how much we don’t understand about the connection between physical movement and the brain.

Future research will need to dig deeper, measuring more pathways, tracking more biomarkers, and following people for longer periods. For now, we have a what without a why: exercise appears to slow or reverse brain aging, even when the usual suspects don’t explain it.

Disclaimer: This article is for informational purposes only and is not intended as medical advice. The study discussed involved healthy adults aged 26-58 under supervised conditions. Before starting any new exercise program, consult with your healthcare provider, especially if you have existing health conditions, have been sedentary, or are taking medications. Individual results may vary, and the mechanisms by which exercise affects brain structure are not fully understood.

Paper Notes Study Limitations

The sample size of 130 participants limited the researchers’ ability to detect smaller effects or test multiple biological pathways. The COVID-19 pandemic increased dropout rates, with 49 participants unable to complete final assessments—though the proportion who dropped out was similar in both groups. People who completed the study had more education than those who didn’t, which could affect how results generalize. The study didn’t track alcohol use, smoking, or other lifestyle factors that influence brain aging. Participants were generally healthy with low cardiovascular disease risk, so the findings might not apply to people with existing health problems.

Funding and Disclosures

The National Institutes of Health and the National Heart, Lung, and Blood Institute funded the research (grant P01 HL040962). Dr. Kirk Erickson consults for MedRhythms, Inc. and Neo Auvra, Inc., but these companies weren’t involved in the study. No other authors reported conflicts of interest.

Publication Details

The study appears in the Journal of Sport and Health Science (2095-2546/2026), published by Elsevier B.V. on behalf of Shanghai University of Sport. The research team included Lu Wan, Cristina Molina-Hidalgo, Mary E. Crisafio, George Grove, Regina L. Leckie, Thomas W. Kamarck, Chaeryon Kang, Mia DeCataldo, Anna L. Marsland, Matthew F. Muldoon, Mark R. Scudder, Javier Rasero, Peter J. Gianaros, and Kirk I. Erickson, representing institutions including AdventHealth Research Institute, Colorado State University, University of Pittsburgh, Washington & Jefferson College, and University of Virginia. The study received IRB approval (ID: 19020218), registered at ClinicalTrials.gov (NCT03841669), with DOI: 10.1016/j.jshs.2025.101079. Recruitment ran from May 2019 to October 2022, with follow-up through February 2024.